Fixed-Time Safe-by-Design Control for Uncertain Active Vehicle Suspension Systems With Nonlinear Reference Dynamics

This article presents a novel fixed-time safe-by-design control for uncertain active vehicle suspension systems (AVSSs) with matched/unmatched disturbances, high energy consumption, input saturations, and asymmetric time-varying constraints on both displacement/velocity. Several asymmetric time-varying barrier Lyapunov functions are carefully constructed to deal with displacement/velocity constraints under the fixed-time convergence framework. Furthermore, a new fixed-time auxiliary state system is proposed to compensate for the saturation effect. It is then rigorously demonstrated that the convergence time is independent of initial state conditions and both the displacement/velocity are always restricted within the asymmetric time-varying ranges. Importantly, by employing beneficial nonlinearities of a bioinspired X-shaped reference model, the burden of high control energy cost can be relaxed compared with traditional controllers. As far as we know, this should be the first attempt to achieve a fixed-time safe-by-design control for AVSSs, which simultaneously considers practical issues including meeting the safety requirements for input saturations and displacement/velocity, achieving fixed-time convergence, maintaining energy efficiency, and rejecting matched/unmatched disturbances. Experimental testing results validate the effectiveness, advantage, and feasibility of the proposed control algorithm, compared to other existing methods.